The FishWorks ShopFish Passage

An Educational Series Presented by the R&E and STEP Programs

In order for fish to utilize habitat in a river or stream, fish need to be able to get there. While that may seemsimple enough, over the last two centuries people have been building barriers to fish throughout the country,especially dams, irrigation diversions and roads. Cumulatively, these barriers have prevented many native fish

species from accessing hundreds of thousands of miles of historical habitat in the U.S. These barriers have had asignificant impact in Oregon since so many of our streams host runs of anadromous fish such as salmon, steelhead,Pacific lamprey and sea-run cutthroat trout that have been cut off from significant amounts of spawning and rear-ing habitat. Resident species such as trout also suffer from stream barriers. Impassable barriers affect how muchhabitat those fish are able to utilize and also limits genetic exchange with other fish of the same species living indifferent parts of the stream and is important for genetically healthy populations.

But in recent years, a great effort has been made to improve fish passage on Oregon streams and rivers, whichincludes repairing old passage facilities that no longer work, upgrading others with the latest technology and creat-ing passage where there was none. In addition, since 2001 Oregon law requires that “the owner or operator of anartificial obstruction located in waters in which native migratory fish are currently or were historically presentmust address fish passage requirements” when improving, adding to, obtaining new permits or abandoning thoseartifical obstructions. Through ODFW Fish Passage Program partnership with the R&E and STEP programs,ODFW continues to be very involved in providing fish passage in the state’s rivers and streams.

DamsMany, but not all, large dams were constructed with fish

passage facilities. Even then, there can be challenges.Some of the most well known examples are the federalhydropower dams on the Columbia and Snake rivers.Although they have fish ladders that successfully passupstream migrating salmon and steelhead, difficulties areencountered by smolts as they migrate downstream to theocean. The slack water in the reservoirs above the damscan slow the smolts’ journey to the sea and others diewhen they are sucked into the dams’ turbines. Solutions tothose problems include increasing spill during criticalsmolt migration periods and using screens and otherdiversion structures to move the small fish around thedam and into the river below.

In other situations, the best approach may be to removethe dam from the river altogether. Such is the case with theSavage Rapids Dam on the Rogue River. Although it has a fish ladder, it never worked very well and in at least oneincident several years ago, thousands of salmon smolts were killed when the system malfunctioned. Savage RapidsDam is slated for removal in 2010 and the irrigation water it diverted will be drawn from the river by pumps.

Providing fish passage on large dams is often a very technical process that requires detailed negotiations withdam owners, various government agencies and other parties. ODFW technical staff are major participants in thesenegotiations.

Irrigation DiversionsSmall irrigation diversions are much more numerous than larger dams on Oregon streams and cumulatively have

a substantial impact on fish populations. These are typically small dams that are closed off during the irrigation

The Savage Rapids Dam on the Rogue River will beremoved in 2010 to improve fish passage.

Fall 2008

season, from spring through fall, and the water is diverted intocanals that deliver it to nearby agricultural fields. Irrigationdiversions pose two challenges to fish. With the headgates closed,fish are not able to pass. In addition, fish may be inadvertentlydiverted from the main stream into the irrigation canals wherethey may eventually die as the water in the ditches dries. Somefish may even be funneled into the fields along with the water.

Fortunately, there many opportunities to improve fish passageat irrigation diversions and ODFW works with farmers andranchers throughout the state to find solutions. This typicallyinvolves construction of a small fish ladder that allows fish toascend the dam along with a screened diversion system to keepthe fish in the main stream channel and away from the irrigationditches.

ODFW also provides irrigators with information on obtaininggrants to help fund fish passage improvements to their irrigationdiversions.

Roads and CulvertsCulverts under roads represent one of the most widespread impediments to fish passage in the state. While cul-

verts may be an efficient and inexpensive way to pass a road over a small creek, they can block off many miles ofotherwise good spawning habitat to salmon and steelhead. This is especially true in forest areas where culvertswere commonly used when building logging roads.

Typically, culverts under roads are relatively small in diame-ter compared to the stream. This causes water to rush thoughthe culvert at a flow rate that may be too fast for fish to swimup. Because there are no rocks, logs and pools inside the cul-vert, there is no place for fish to rest as they try to ascend it. Inaddition, as water pours out the downstream side of the cul-vert, it wears away the pool below it, and eventually the jumpinto the culvert may be too high, especially for the smallerjuvenile fish.

Often, the best solution is to replace the culvert with a bridgeand restore the natural stream habitat beneath it. Anotherapproach is to replace the old culvert with a large, bottomlessculvert. The large size permits the stream to flow at naturalrates and without a bottom to the culvert, the originalstreambed can be utilized.

R&E, STEP and Fish Passage The Fish Restoration and Enhancement Program and Salmon Trout Enhancement Program are both heavilyinvolved in fish passage improvements. One of the best examples of these two programs working together on a fishpassage project was on Fall Creek on the Coos River system where a large waterfall blocked steelhead and salmonfrom reaching eight miles of prime habitat. Nearly 100 STEP volunteers constructed a 30-jump fish ladder over thefalls. R&E contributed a $28,600 grant to the project. More recently, R&E helped fund major fish passage improve-ments at irrigation diversions on the Chewuacan River and STEP volunteers removed a small fish-blocking dam ona tributary of the East Fork Trask River. Both STEP and R&E will continue to make fish passage improvements onOregon’s rivers and streams a top priority.

For more information on the ODFW Fish Passage Program, contact Greg Apke, Fish Passage ProgramCoordinator at 503-947-6228.

For more information on the R&E Program contactR&E Program Coordinator Laura Tesler, at 503-947-6259. For STEP, contact Program Coordinator TomFriesen at 503-947-6232.

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An irrigation diversion in Harney County thathas been fitted with a fish ladder and screen tokeep fish in the main channel.

A large culvert utilizing a stream’s natural bedprovides much better upstream passage for fish.